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<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    
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<script>
    var x = prompt('输入一个数字x');
    var y = prompt('输入一个数字y');
    var z = x;
    var y = z;
    var x = y;
    alert(x+y)
</script>